Electrical condenser and process for making the same



Jan. l, 1924 1,479,315

G. W. PICKARD ELECTRICAL GONDENSER AND PROCESS FORv MAKING THE SAME Filed Jan. 12, 1921 nvemtoz Patented Jan. l, 1924.

UNITED STATES PATENT OFFICE.

GREENLEAF WHITTIER PICKARD. 0F. NEWTON CENTER, MASSACHUSETTS, ASSIGNOB TO WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A

CORPORATION OF NEW YORK.

ELECTRICAL CONDENSER AND PROCESS FOR MAKING THE SAME.

Application filed January 12. 1921.

To nl] whom it may confiera.'

Bc it known that I, (inunNLuAr )Vnrr'rncn IIcKARn, a citizen of thc United Sta-tes of America, and a resident of Newton Center, State of Massachusetts, have invented certain new and useful Improvements in Flectrical Condensers and Processes for Making the Same. the principles of which arel set forth in the followingspecification and accompanying drawing, which disclose the form of the invention which I now consider to be the best. of the various forms in which the principles of the invention may be embodied.

rThis invention relates to electrical condensers and a process for making the same.

In the manufacture of condenscrs, it is preferable to secure intimate Contact between thc metal conductors and their intervening dielectric. whether of the sheet or jar type.y to exclude air and other substances which would otherwise form with the desired dielectric an undesirable composite dielectric having large losses. This intimate contact. can be obtained by coating the dielectric sheets with a metal deposit instead of using metal foil.

An object of the invention is to provide methods and means for commercially and practically making sheet condensers by forming metallic depositions on the dielectrics.

Another object of the invention is to provide a durable, compact and commerciallypractical condenser of the above type in which the several deposits are alternatel.v electrically connected in an efficient manner.

The metal. such assilver, tin, copper or lead in a finely divided state may be depositedcn the dielectric. which may consist of any suitable material such as mica., by methods such as l) B v the Schoop process in which metal is deposited on the dielectric by blowing metal vapor formed from a heated filament of' wire against the dielectric.

(2) By chemical deposition from electrolyt'ic. solution, which may be considered a deposition of metal in a finely divided state.

3) By forming metal deposits from finely divided metal suspended in a suitable medium such as varnish on the dielectric by Serial N0. 436,650.

spraying, painting` or otherwise treating the dielectric.

(4) By any electroplating method, having first made the surface conducting as by a thin chemical deposit of metal, or by rubbing on graphite or other conductor.

In the accompanying drawing,

Figure 1 is a plan view of a sheet of dielectric showing a deposit of metal thereon upon both sides.

Fig. 2 is a sectional elevation, with thickncsses exaggerated for the sake of clearness, illustrating the application of metal deposits to both sides of a sheet of dielectric.

n Fig. 3 is a plan view of a dielectric sheet illustrating the application of a deposit of metal to one side thereof.

Fig. 4 is a sectional elevation, With thicknesses exaggerated, illustrating the application of a metal deposit to one side of the dielectric.

Fig. 5 is a sectional elevation, with thicknesscs exaggerated for sake of clcarness, of a condenser or section built up of metal deposited sheetsas illustrated in Figs. 1 and 2.

Fig. 6 is a sectional elevation, with thicknesses exaggerated for the sake of clearness, of a condenser or section built up of metal deposited sheets as illustrated in Figs 3 and 4.

Fig. 7 is a plan view illustrating the application of the metal deposit to a modified shape of dielectric; and

Fig. 8 is a sectional elevation illustrating the assembly of several sheets such as shown in Fig. 7 to form a condenser or section, thicknesses being exaggerated for the sake of clearness.

In depositing metal on the sheets of 'dielectric, a margin free of metal is provided on three edges, where the sheet has four sides. vof each sheet of dielectric, the metaldeposit coming to the edge on the fourth side. The present invention is applicable to sheets of dielectric having different shapes, however. vWhere a deposit is placed on both sides as illustrated in F igs. 1 and 2, margins are provided on both surfaces, but the metal deposits on opposite surfaces of the dielectric come to opposite edges.

' Referring to Figs. 1 and 2, which illustrate an application of the invention to a rectangular sheet of dielectric, the dielectric l may consist of any suitable material preferably mica, having a thickness preferably between l and 5 mils. Metal deposits, films or layers 2 and 3 are placed on opposite surfaces of the dielectric 1 in such a manner as to leave margins 4 along three edges thereof on each side. -Unlike constructions employing metal foil, the metal deposits on opposite surfaces of thedielectric 1 not only extend to opposite edges 5 and 6 of the dielectric respectively, but also, in the particular embodiment herein described, over, around or upon such edges 5 and (i as illustrated at 7. ln some cases, dielectric la may have a metal deposit, film or layer 2a on one side only as illustrated in Figs. 3 and 4 with the usual margins 4a and extending over one edge as illustrated at 7 a.

The metal is deposited uniformly and electrically continuously over 'the dielectric except on the margins 4 byprocesses such as those enumerated above. During such deposition, a mask is used to prevent the deposition of metal on such portions of the dielecgins 4 above mentioned. For instance, a

Vshield is inserted between the dielectric and metal sprayer, where a sprayer is used or where the Schoop process is used. lVhere chemical or other deposition of metal is employed, the margins should first be coated with a suitable Wax or with oil to prevent metal deposition thereon, which Wax or oil can later be melted or washed off, removing any metal deposited thereon. When electroplating, only the desired area is to be made conducting, and no mask or coating is necessary, as metal will not deposit on non-conducting parts of the sheets.

The edges 5 and 6 of the dielectric usually and preferably are coated with axmetal deposition 7 when the surfaces of the dielectric are coated in a case where, as in Fig. 1, the coating or deposit is made to extend to the edge of one portion of the dielectric. This is becausel the depositions on the surfaces when so made to an edge tend to round around the exposed opposite edges 5 and 6. It is not necessary, however, that the coating or deposit extend around from the surface and over the edge. Such rounding over the edges is shown in the drawings not only because such result is the normal tendency, but because it is the preferred form.

After a sufficient number of dielectric sheets l or la have been treated as above described, either on both sides as illustrated in Figs. l and 2 or on one side as illustrated in Figs. 3 and 4,"they are built up into a stack or unit of any desired capacity as illustrated either in Fig. 5 or Fig. 6.

Fig. 5 illustrates a stack of dielectric sheets leach having metaldeposits on both sides.

The sheets are stacked so that each pair of adjacent and contacting metal deposits have their edges 7 at the same side of the stack although successive pairs have such edges 7 alternately at opposite sides as illustrated.

'InV Fig. 5, as in other figures, the thickness of the dielectric and metal deposits is exaggerated and in practice such dielectric and deposits are very thin and uniform. The edges 7 and their integral deposits 2 and 3 at each side of the condenser are then electrically connected together by co\f'ering, coating or .spraying all the edges 7 at opposite sides of the condenser, or at electrically separated 'or spaced portions of the stack accordmg to the construction or shape of the stack, this coating consisting permissively of finely divided metal applied. by methods such as those above enun'ierated; but this connecting together of the edge deposits may be effected by soldering all the edges 7 forming connections 8 and 9 having close electrical contact with the edges 7 as illustrated at opposite lsides of the condenser. The reference characters 8 and 9 illustrate connecting conductors (although exaggerated in thickness) formed by the application of a metallic substance of such a nature as to properly connect the several metal edge deposits into a close electrical contact, and completing a condenser 'having metal conductors (the deposits) of opposite polarity. In practice, since adjacent dielectrics l are close together, forming a restricted space l0 where unobstructed by metal deposits, when the connections 8 and 9 are formed, by any of the methods above mentioned, there is very little likelihood of the margins 4, Fig. 5, of the restricted space 10, becoming covered with metal and thus short-circuiting the condenser. However, where high efiiciency is desired, especially where the hereindescribed process is employed in making condensers for .use inphigh power work, such as in radio transmitting condensers, such spaces 10 may be filled with insulating material, as shown, before connections are made, and thus protected by this insulating material which may oe paraffin or varnish as hereinafter described. In the type of condenser illustrated in Fig. 5, pressure so important in condensers employing metal foil, is not necessary in order to obtain intimate contact, as the metal deposits are already in such intimate contact with their dielectric and each pair of adjacent contacting metal deposits are at the same potential, being connected together at 8 or 9. Pressure, however, may be employed to compact the stack and reduce its size. In some cases, it may be advantageousto formvby any of the aboveenumerated methods a soft metal deposit as of lead on one dielectric, and then apply pressure between this soft deposit and another soft deposit on the surface of an adjacent dielectric. The advantage of this is the mechanical one of obtaining a smaller stack.

In Fig. 6 is illustrated a stack built up of sheets 1 having a deposition, la er or film of metal 2 on one side only and ormed as above described. Such sheets are superimposed as illustrated with successive metal deposits arranged to extend alternately from opposite ends or from electrically separate or spaced portions of the stack. Thus a deposited layer in each instance engages an uncoated surface of a dielectric. In this form, it is preferable to apply a high pressure, of' the order of 1,00() pounds to a square inch, to secure the desired intimate contact and exclude air from between any dielectric and the metal deposit on the adjacent dielectric in contact therewith as indicated at 11. It is also preferable in such cases to make the metal deposit of some soft metal such as lead, so that intimate contact with thc opposing mica may be b' tained despite the latter irregularities of surface. In the form of Fig. 6, as in Fig. 5, it may be advantageous to form a soft metal deposit and then apply pressure. The object in this instance is not only to consolidate the stack into small compass, but

also to secure intimate contact between the deposit: and the uncoated adjacent surface of the dielectric, thereby pressing air out laterally and highly compressing any air which might not be pressed out, all whereby brush discharges are prevented.

The stacks illustrated in Figs. 5 and 6 may be treated with some insulating material such as paraffin or varnish to protect the margins before the connections are made and as hereinafter described, and then connected by the methods described in connection with Fig. 5, or the treatment with insulating material may be deferred until after connections are made, according to the use to which the condenser is to be put. For instance, magneto condensers do not require the rcfinen'ients of care that radio transmitting condensers do.

The condensers of Figs. 5 and 6 above described and also of Fig. 8 may be treated with an insulating material such as paraffin, resin or varnish either before or after the connections 8 and 9 are made, according to requirements, in order to remove air and protect the margins and prevent brushing. In cases where such treatment is performed before the connections are made, thus covering the margins il, any adhering wax or varnish on parts to which the conductors 8 and 9 are applied would not thereafter prevent the proper making cf connections 8 and 9 as such wax, etc., would be melted away by the applicationk of the connections. In fact, a substance like resin would act usefully as a flux in cases where solder is used. Condcnsers employing high voltages should be carefully treated, preferably as disclosed in my copending application Serial Number 380,91 9, filed 12 May, 1920,- with insulating material with use of vacuum to remove air and prevent brushing conditions, either beforeor after the connections are made according to requirements. Treatment of magneto condensers with insulating material having adhesive properties also forms the condensers into a solid mass. Several such sections as shown in Figs. 5 and 6 may be stacked and connected together in any suitable manner, in series or otherwise.

In Figs 7 and 8 is illustrated a mica sheet 1* provided with notches 12 at electrically separated or spaced portions of the stack or as here illustrated at opposite ends into which notches extend the edges 7b of the metal deposits, films or layers 2b and 3b on opposite sides of the dielectric 1b. The metal deposits are otherwise made and arranged just as in the other forms already described. lVhen several of such sheets 1b with their metal deposits 2b an( 3" are superimposed and stacked as illustrated in Fig. 8, the notches 1 2 are aligned to form grooves 13 at opposite ends of the stack or unit in which solder may be conveniently placed and contained by the grooves 13 for making electrical connections 8 and 9 either before or after the wax treatment described. The thicknesses in Fig. 8 are exaggerated. In actual constructions, well defined grooves 13 will be formed by stacking up a number of thin sheets 1b with their thin metal deposits, and good electrical contact may be secured by filling such grooves 13 with solder covering the edges 7b of the condenser or unit, and electrically connecting alternate sheets at opposite ends. After the above-described steps, the condensers may be placed in a permanent clamp or casing, or both.

The condensers made in accordance with the present invention are compact and rigid and have their alternating dielectrics and metal deposits in intimate contact and have a close electrical contact and connection between -the deposits of each polarity, forming very eflicient condensers.

It is to be understood that the invention is not limited to the embodiments and features specifically shown and described herelll!) comprises a dielectric sheet having a sheet of inet-a1 integrally united with a central portion of a side surface thereof wlthln its edges, said metal sheet extending around and over a portion of the edge of the dielectric sheet into a. position beyond the surface of the dielectric sheet.

3. An electrical condenser stack comprising dielectric sheets each of which has a metal sheet integrally united with a central portion of its surface within its edge but extending to a portion of said edge, a plurality of such dielectric sheets being so arranged in the stack that the said extended parts of the integrally united metal sheets are grouped in the vicinity otoneanother; and a metal portion located outside the stack, integrally united with said extended parts of the metal sheets, and constituting a continuous electrical conductor in electrical connection with all the integral metal sheets which have'their extended portions in the same neighborhood.

4. An electrical condenser stack; which comprises a plurality of dielectric sheets each of which has two metal sheets integrally united respectively with two sides, and a margin free of metal, said metal sheets extending on opposite sides of the dielectric sheets to portions of the edge thereof which are spaced from one another; said dielectric sheets and integrally united metal sheets being piled in the stack in reverse 'order in respect of the metal sheets and margins whereby the portionsof the metal sheets which extend to the edges lie adjacent to one another, alternate pairs of such metal sheets extend to opposite sides of the stack, and the metal-free margins of successivel dielectric sheets are registered with one another.

5. In an electrical condenser, a stack comprising a plurality of sheets of dielectric having metal deposits thereon extending alternately to edges of the sheets at portions of the stack spaced from one another and each sheet of dielectric having a margin free of metal, and metal deposits applied over said vspaced portions of the stack electrically connecting with close contact the metal deposits forming a condenser having groups of deposits of opposite polarity.

6. In an electrica-l condenser, a stack comprising a plurality of sheets of dielectric, each having a metal deposit'thereon extending to and upon an edge of the dielectric and having a margin of dielectric along a remaining edge, ,the metal coated edges o'f the dielectrics being arranged alternately at portions of the stack spaced from one another, and metal deposits on said spaced portions of the stack connecting the metal coated edges at said portions forming a condenser having groups of metal deposits of opposite polarity.

7. In an electrical condenser, a stack comprising a plurality of sheets of dielectric, each having a metal deposit thereon 'extending to and upon an edge of the dielectric and having a margin of dielectric along a remaining edge. the metal coated edges of the dielectrics being arranged. alternately at portions of the stack spaced from one another, metal deposits on said spaced portions of the stack connecting the metal coated edges at said spaced portions forming a condenser having groups of metal deposits of opposite polarity, and insulating material covering said condenser.

8.' In an electrical condenser, a. stack comprising a plurality of sheets of dielectric, each having met-al deposits thereon upon opposite sides extending to and upon the edges at opposite ends of the dielectric and having a margini of dielectric along the remaining edges upon each side, the metal coated edges of the dielectrics being arranged alternately at opposite sides of the stack with the metal coated edges of adjacent deposits adjacent to each other, and metal deposits upon said opposite sides of the stack connecting the metal coated edges at said opposite sides otv the stack forming a condenser having groups of metal deposits metal deposits on said spaced portions of.

the stack connecting the metal coated edges at said spaced "portions in the' grooves formed by said notches and forming a condenser having groups of metal deposits of opposite polarity.

10. vIn an electrical condenser, a stack comprising thin sheets of mica dielectric having 'in intimate contact therewith thin metal lilms deposited thereon from a nelydivided state, said deposits alternately extending to and upon certain edges of the dielectrics at portions of the stack spaced from one another, uncoated margins remaining along the other edges of the dielectrics, and metal deposits on said spaced portions forming a close electrical 'contact with and connection between the metal coated edges at said spaced portions, forming a condenser having groups of deposits Vof-opposite polarity.

1l. An electrical condenser stack which comprises a plurality of dielectric sheets each of which has a sheet of metal integrally united with a portion of its surface and stack of sieets; said dielectric sheets andintegral metal -sheets being disposed in the stack in such wise that the edge metals of some of the dielectric sheets are located at a portion of the stack remote from the edge metals of other sheets; the metal edges which are grouped together at one portion .of the stack being integrally united with a metal member outside the stack and constituting a continuous electrical conductor which thereby electrically connects together all the integrally united metal sheets of which such metal edges are parts; and the metal edges which are grouped together at another portion of the stack being likewise integrally united with another metal member constituting a continuous electrical conductor connecting together all such metal edges.

12. The herein-described method of making electrical condensers which consists in depositing electrically continuous layers of metal upon sheets of dielectric up to and upon certain edges thereof by the application of metal in a finely divided state leaving margins along remaining edges free of metal, building a stack of such metal coated sheets of dielectric with the coated edges arranged alternately at portions of the stack spaced from one another, and then electrically connecting the metal edges at said spaced portions by covering the same with a metallic Substance in such form as to make metallic depositions thereon, substantially as described.

13. The herein-described method of making electrical condensers which consists in depositing electrically continuous layers of metal upon sheets of dielectric by the application of metal in a finely divided state to central parts of the sheets within their edges but extending to a certain portion of the edge of each sheet, while leaving free of metal a margin along the remaining portions of the edges of the dielectric sheets; building a stack of such metal-coated dielectric sheets; treating the stack with insulating material; and making connections between la 7ers of metal, via the portions thereof which extend to the edges of the dielectrics, to form a condenser having two groups of metal layers respectively of opposite polarity, substantially as described.

14. The herein-described method of making electrical condensers, which consists in de ositing upon sheets of dielectric electrica ly continuous layers of metal extendin to edges thereof by the application of meta in a finely divided state and leaving margins free `of metal along remaining edges of the sheets of dielectric, building a stack of such metal coated sheets with layers of metal extending alternately to portions of the stack spaced from one another, and then applying a metallic substance over said spaced portions to electrically connect the layers of each group of alternately extending metal layers with a close electrical contact, Substantially as described.

15. The herein-described method of making electrical condensers, which consists in depositing upon sheets of dielectric electrically continuous layers of metal extending to certain edges thereof by the application of metal in a finely divided state leaving margins free of metal along remaining edges of the sheets, building a stack of such metal coated sheets with layers of metal extending alternately to portions of the stack spaced from one another, treating said stack with insulating material to protect the margins, and then applying a metallic substance over said spaced portions to electrically connect the layers of each group of alternately extending metal layers with a close electrical contact, substantially as described.

16. An electrical condenser stack comprising dielectric sheets, each of which has a metal sheet integrally united with a part of its surface and extending to one portion of the edge thereof but not to another portion of such edge, said compound sheets being arranged in the stack in pairs whereof the extending metal portions of one pair lie in contact with the extending metal portions of the pairs on opposite sides of said given pair; and whereof said non-covered surfaces of the dielectric sheets of o'ne pair lie adjacent to like surfaces of the dielectric sheets of the pairs on opposite sides of said given pair, and form spaces near theedges of and between successive pairs; insulating material in said spaces; said contacting extending metal portions being electrically connected together in two separate groups to constitute the two terminals of the condenser.

GREENLEAF WHITTIER PICKLRD. 

